In the state of the art are well-known self-locking cable tie straps for binding together in a bundle wires or cables for the realization of harnesses of any kind.
The cable tie straps according to the known art comprise a head part provided with a retaining tooth or pawl, sometimes realized with a metallic insert, arranged to cooperate with a flexible member integral with the head and provided with a toothing on one side arranged for engaging in an irreversible way the retaining tooth or pawl at the moment of the fastening of the bundle of cables and wires. These tie straps according to the prior art have the tooth or pawl in the head that operate in a unidirectional way and are arranged to cooperate with the toothing on the flexible member or tail that is provided with the toothing on one side only.
This known construction of the self-locking tie straps with an irreversible locking entails that owing to the asymmetrical structure of the same, at the moment of their application for the binding of cables or wires it is necessary to pay attention to the direction of insertion of the flexible member or tail to ensure correct engagement and locking with the head.
There are also known members for the temporary locking of electrical wires with a releasable locking with a symmetrical structure used for the temporary locking of electrical cords of electrical or electronic apparatus during the packaging, having a symmetrical structure that is however not suitable for assemblies of the industrial type and that do not show the capabilities of locking and safety of locking of the cable tie straps for industrial use mentioned above.
It is also to be remarked that in the cable tie straps for industrial use to which the present invention is mainly referred, the known asymmetrical structure does not shown inconveniences when these straps are applied by hand; a minimum amount of attention on the part of the operator is sufficient.
However, in the case of binding machines of the industrial type, the asymmetry of the known cable tie straps entails several serious inconveniences. The cable tie straps according to the prior art owing to the asymmetry cause a partially free binding at the base of connection of the flexible part or tail with the head part. This free part at the base of the head assumes a more or less acute angle in relation to the pull exerted at the binding and related to the diameter of the cables, straining the material of the strap at the connection part with the head possible development of nicks or breakage at the connection base.
The straps according to the prior art are provided as tapes to allow the feeding of the tapes to an automatic binding tool.
The asymmetrical shape of the straps according to the prior art fed from an auxiliary distributor is the main origin of jamming of the mechanism of the auxiliary distributor as well as of the binding tool and the feeding conduit, since the feeding method is based on a transfer of the strap along a closed path by fluid propulsion (compressed air). The orientation of the strap is consequently extremely important to ensure the receiving of the strap within the binding tool into a correct position.
In order to ensure the correct orientation, systems according to the prior art use a flexible tube having a square or rectangular cross section that reproduces the outline of the head of the strap and consequently the strap inserted into an auxiliary device of the distributor is "shot" along the piping by means of a jet of air, maintaining its orientation.
This method that seems correct became critical and causes inconvenience when there is impressed a torsion to the square section piping or when the piping itself is bent with a radius shorter than a given limit.